Method for uniting thread ends

ABSTRACT

Method of uniting the ends of thermoplastic threads or yarns by twisting the ends over a short length with the twisted length being clamped and held under tension and applying heat to a relatively small area of the twisted length so as to melt and bond the threads together as they are simultaneously caused to untwist under the release of tension. The method essentially includes two clamping means adapted to receive and hold the twisted length of threads, and a heating element preferably positioned immediately adjacent one of the clamping means and adapted to melt and bond the ends of the thread.

United States Patent [72] Inventor Richard Munzner Obernburg am Main, Germany [21] Appl. No. 800,049 [22] Filed Feb. 18, 1969 [45] Patented Oct. 26, 1971 [73] Assignee Glanzstoff AG Wuppertal, Germany 32] Priority Feb. 24, 1968 [3 3 Germany [31] P17104603 [5 4] METHOD FOR UNITING THREAD ENDS Primary Examiner-Carl D. Quarforth Assistanl Examiner-Gary G. Solyst Attorney-Johnston, Root, O'Keeffe, Keil, Thompson &

Shurtleff ABSTRACT: Method of uniting the ends of thermoplastic threads or yarns by twisting the ends over a short length with the twisted length being clamped and held under tension and applying heat to a relatively small area of the twisted length so as to melt and bond the threads together as they are simultaneously caused to untwist under the release of tension. The method essentially includes two clamping means adapted to receive and hold the twisted length of threads, and a heating element preferably positioned immediately adjacent one of the clamping means and adapted to melt and bond the ends of the thread.

PATENTEDBU 26 I9" I 3,615,991

INVENTOR.

METHOD FOR UNITING THREAD ENDS This invention generally relates to a method and an apparatus for uniting or melt-bonding the ends of yarns or threads composed of a thennoplastic filamentary material. In processes for the treatment of threads or yarns and also with the further processing of the threads or yarns to form a textile product, i.e. fabric or the like, it is always necessary for the last end of a thread package to be connected to the leading end of the following package. This connection of one yarn end to another must be strong enough to withstand the stresses or tension which occurs during any further processing of the continuous thread or yarn. However, the connection of the yarn ends must also be easily and quickly produced and should not have any deleterious effect, either during the processing or in the finished textile pattern. It has not previously been possible to comply with these requirements in a satisfactory manner. For example, with voluminous carpet yarns, which usually consist of a plurality of differently colored individual yarns or threads assembled into a multi-thread yarn, a conventional procedure for achieving a yarn connection has been to separate the yarn components, i.e. the individual threads of the same color, from one another and then connect each colored thread with one another individually by splicing knots arranged in staggered relation.

It is also known to weld or melt-bond the ends of such multiple thread yams by means of an electric heating arrangement, e.g. as disclosed in Belgian Pat. No. 633,747.

This known apparatus essentially includes a device for moistening the threads, an electrically heated clamping device in which the threads are welded or bonded together, and a severing device in order to cut off the ends which have become free after the welding operation is concluded. The two thread ends to be welded are first of all wetted by hand in the moistening arrangement and thereafter are pressed between the clamping jaws and welded. While the welded thread is held in the clamping device, the ends of the thread are cut of? by means of the cutter or severing device, whereupon the welded or bonded thread can then be extracted from the clamping device.

In addition to a very complicated manipulation of the thread ends, this known apparatus and procedure has the disadvantage that the quality of the bonded union depends to a high degree on the period of time during which the threads to be united are held in the clamping device. Individual connections in different lengths of thread consequently show great differences in quality and appearance. Furthermore, experience has shown that the severing device cannot completely eliminate projecting thread ends which then remain and have a deleterious effect during the further processing of the thread into textile fabrics and in the finished pattern of these fabrics. This same objection arises where the thread ends are simply knotted or spliced.

One object of the present invention is to provide a method and apparatus for the rapid and efiective welding or meltbonding of thread ends which avoids prior difficulties and yet can be carried out in a relatively simple manner.

Another object of the invention is to melt-bond thread ends with a minimum of waste material and a substantially complete absence of projecting or free ends at the point of union.

Other objects and advantages of the invention will become more apparent upon consideration of the following detailed disclosure.

It has now been found, in accordance with the invention, that the ends of individual yarns or threads, e.g. from one thread package to the next during a textile operation, can be effectively united to one another by the steps which comprise: placing the ends of the threads to be united together in parallel relationship with the ends extending in the same direction; twisting the threads over a short length adjacent the ends thereof with an amount or degree of twist sufficient to cause the threads to untwist under the release of longitudinal tension; clamping the twisted short length of threads at either end thereof under longitudinal tension; and applying heat to a selected intermediate area or portion of the twisted length sufficient to temporarily melt the individual threads and simultaneously cause them to untwist under the resulting release of tension.

in essence, the melt-bonding of the thread ends is accomplished as the twisted threads rotate and unwind under the torsional stress imparted by the original twisting of the juxtaposed threads and held in place by clamping the short twisted length. Since heat is most easily applied only to one side of the twisted threads, preferably in direct contact with a suitable heating element, the melt-bonding operation actually has the effect of melting through the twisted threads so as to release the longitudinal tension thereon and cause them to untwist under the influence of the torsional stress. Since the individual threads are in contact during this rotation, they become welded together as soon as they resolidify at a short distance from the heating element.

Some care must be exercised as to the amount of heat supplied to the twisted threads at the point of welding to avoid overheating the threads and causing severe damage thereto, and in general, it is sufficient to regulate the heating element so as to bring the threads in contact therewith or at least in close proximity thereto to just above the melting point or softening temperature of the particular thermoplastic material, preferably not more than about 280 C. above this softening temperature.

The clamped length of the twisted threads, the amount of twist and the specific area over which heat is applied will naturally vary to some extent depending upon the size or denier of the individual thread or yarn ends being united, the number of individual filaments in the thread or yarn and similar factors. However, the method of the invention is generally applicable to a wide range of thermoplastic threads or yarns especially those composed of continuous monofilaments or multifilaments but also staple fiber threads and yarns and even composite yarns.

In working with many different threads or yarns, e.g. with yarn counts or numbers of anywhere from 200 to 10,000 denier, and from 2 to 10 individual filaments, it has generally been found that the initially twisted length of threads should be clamped between positions spaced apart by a distance of about 2 to 10 cm. and preferably 4 to 8 cm. Also, it is usually sufficient to impart a twist of about 1 to 4 turns/cm. in order to achieve the desired amount of torsional stress. In all cases, a few preliminary tests suffice to accurately determine the most effective amount of twist for a given length of the threads between clamping positions.

The intermediate area or portion of the twisted length at which heat is applied, e.g. by means of an electrical resistance heating element, should normally be maintained within limits of about 0.5 to 4 mm. and preferably about 2 mm. or less. Heating of an overly extended portion of the twisted length should be avoided and the minimum length to which heat is applied will depend for the most part on the size and construction of the heating element. Although this heating element may be in direct contact with the twisted length of threads, it should not in itself cause a clamping or restriction on the threads which would interfere with their unwinding or untwisting at the point of heat application.

The best results are achieved if heat is applied directly adjacent to or at a relatively short interval from the clamping position which is most remote from the terminal or free ends of the threads. Thus, the heating zone or area of heat application is preferably about 1 cm. or less from this remote clamping position.

After the untwisting threads are completely separated during the melt-bonding operation, i.e. at the point of melting, the ends are bonded together when a relatively short length of the two severed portions, each containing the two threads. drop downwardly and thus move completely away from the heat supply so as to rapidly solidify. By heating only a very narrow or restricted portion of the initially twisted threads, the bonding occurs only a very short distance along the united threads. This does not cause any significant projection of these melted and reunited thread ends outside of the normal linear path of the threads although it may impart a slightly crimped appearance at the point of union which can hardly be observed, if at all, in subsequent operations or in completed fabric products.

it is also a purpose of the invention to provide apparatus for the heat welding of the ends of threads or yarns composed of thermoplastic filaments. Such apparatus includes a pair of clamping means spaced from each other and adapted to receive and hold a length of twisted threads under tension, each clamping means comprising two jaw members of which at least one is pivotally mounted and resiliently urged toward the other to tightly hold the twisted strand of threads therebetween. The apparatus further includes an electrical resistance heating element arranged or positioned immediately adjacent one of the clamping means at a point in close proximity thereto at which it will heat and melt a short length, e.g. up to about 4 mm. and preferably 0.5 to 2 mm., of the twisted threads when held under tension between the two clamping means. The heating element is preferably adjustably mounted so that it can be moved toward and into direct contact with the length of twisted threads, thereby permitting a rapid local heating and melt-bonding of the twisted threads.

An especially preferred embodiment of the apparatus is set forth in the accompanying drawing in which:

FIG. 1 is a side elevational view of the apparatus with an enclosure or housing shown in broken lines and certain elements being schematically represented;

HO. 2 is a top plan view of the same apparatus with the housing omitted; and

FIG. 3 is an enlarged partial side elevational view of one clamping means illustrating a thread groove therein which holds the twisted threads.

Referring now to the drawing, especially FIGS. 1 and 2, a base plate or supporting frame 1 carries two identical clamping devices 2, each of which is made up of the jaw members 3 and 4. Both jaws are constructed of a plurality of sheet metal plates 3a, 3b, 3c and 4a, 4b, respectively, separated by similar base shims 5 and 6. In this particular embodiment, the jaw 3 has three plates and the jaw 4 has two plates which are interconnected with their base shims 5 and 6, respectively, by means of suitable rivets or bolts 7. The upper portion of these plates are likewise preferably separated and interconnected by the top shims 8 and 9 and the rivets 10 (as shown by dotted lines and rivet positions in FIG. 1 but intentionally omitted in FIG. 2). The plates of the jaw 4 project into the slots formed by the shims 5 of jaw 3, and conversely, the intermediate plate 3b of jaw 3 projects into the slot formed by shim 6 of jaw 4.

The jaws 4 are provided with an extended arm 1! which carries a downwardly projecting stud 12 which together with the stud 13 on the base plate 1 holds in place a helical spring 14. The resilient clamping force of the jaws or clamping means is furnished by this helical spring 14. Thus, the jaw members 3 are tightly screwed or bolted to the base frame 1, e.g. by means of bolts 15. On the other hand, the jaw members 4 are pivotally mounted to the base frame 1 by means of a pin 16, so that the jaw will rotate or reciprocate in the direction indicated by the double-headed arrow. The helical spring 14 then urges jaw 4 into a closed clamping position against jaw 3 as indicated in all of the figures of the drawing.

This arrangement of the jaws not only permits a secure clamping of a length of twisted threads T therebetween but also provides a rapid and simple means of inserting two parallel and twisted threads or yarns into the device so as to be immediately clamped under tension. Thus, the jaw members 3 and 4 are so constructed as to present oppositely disposed thread contacting surfaces or facing edges 17 and 18, respectively, which are displaced at an acute angle from each other, thereby providing a V-shaped slot capable of being resiliently enlarged as a length of twisted threads is manually wedged or received therebetween.

In order to for the position of the twisted length of thread ends in the apparatus, it is especially advantageous to provide grooved means extending transversely or laterally across the thread contacting face of at least one of the opposed jaws of each clamping member. A specific clamping position of the twisted thread length is thus ensured, for example, by means of U-shaped notches, grooves or slots 19 and 20 cut or machined inwardly from the leading or face edge of each of the plates of the jaws 3 and 4, these slots then forming a thread receiving groove or series of grooved openings through both clamping members at locations in alignment with the linear path of the length of twisted threads to be held under tension, and these slots being so arranged as to completely encircle or enclose the threads when the jaws are resiliently urged into their clamping position.

The length of twisted threads T is thus clamped directly within the opposing slots or grooves 19 and 20 so as to always fall in the same linear path extending directly through the heating zone of the apparatus. Also, once held in this groove, there is no tendency for the threads to become dislodged.

The heating element for welding together the two threads or yam-ends T and T is best provided by an electrical resistance element or wire 21, which is preferably composed of a platinum alloy characterized by a relatively long life in the welding or heat-bonding process. The heating wire 21 is held by two hollow pins 22 and 23 through which lead wires 24 and 25 provide the necessary electrical current. The pin 22 and/or the pin 23 can be movably clamped in a supporting block 26, for example, by means of the tightening screw 27 so as to move the wire into close proximity or direct contact with the linear path of the threads T. In general, the heating wire should be located within l-2 mm. of the twisted threads, but preferably contacts the outer surface of the threads tangentially. The pin holder or block 26 can be securely mounted on the base 1 by means of screws or bolts 28 (see FIG. 2).

The heating element or wire 21 is positioned adjacent to one of the clamping members, preferably at a distance of about 1 cm. or less, and thus provides a localized heating zone which covers only a very short area close to one end of the twisted and clamped length of threads. It is also desirable to arrange the heating wire in such a manner that it cannot be disturbed when the twisted threads are inserted into the clamping device, i.e. directly below the thread position or to one side at an angle as shown in the drawing. in this way, the heating wire 21 and twisted threads T can be very accurately positioned with reference to each other.

The clamping of the twisted threads T in the thread groove or coacting slots 19 and 20 of the individual opposed pairs of jaws is shown in enlarged detail in FIG. 3. Although the twisted threads are firmly held in this clamping position of the jaws, it is normally possible to longitudinally withdraw the severed lengths of threads after melt-bonding is completed without damage to the bonding of the thread ends. If desired, however, means can be provided (not shown) to slightly release the clamping pressure during this withdrawal or the jaws can be slightly separated by hand to facilitate a rapid withdrawal.

The clamping apparatus is advantageously arranged within a protective housing or shell 29 which completely encloses the clamping means and the heating element with its supporting structure except for a thread-insertion slot 30 which generally corresponds to the open or thread-receiving position of the clamping jaws 3 and 4. There are usually a relatively large number of working positions combined in one machine for handling the processing of threads or yarns, but it is unusual for the threads to run out and require melt-bonding of the ends simultaneously at several working positions. it is therefore sufficient to provide a single melt-bonding device for a large number of working positions. The device is thus advantageously arranged on a rail or the like, so that it can be easily and quickly moved from one working position to the other. Thus, the base 1 of the apparatus can be easily carried on a movable carriage.

In using the apparatus to carry out the process of the invention, the thread end from a depleted spool or similar thread package and the thread end from a fresh spool can be brought together in a parallel or juxtaposed position and twisted together by hand, the terminal or free ends of both threads pointing in the same direction. This manual twisting of the threads takes place over a length which is somewhat greater than the distance between the two clamping positions so that the twisted threads can be held under tension as they are introduced into the clamping jaws so as to become engaged and clamped in the thread grooves 19 and 20. On the other hand, it is also possible to first clamp the parallel threads between one pair of jaws and then twist the threads together and applying tension as they are inserted into the other pair of jaws.

Once the threads are clamped, e.g. as shown in FIG. 2, the individual threads T and T extend from their individual spool positions and run into the apparatus through one pair of jaws. A terminal length of the ends of the threads projects a short distance out of the jaws at the other side of the apparatus, and the length of thread from the heating element to these terminal ends is eventually melted off or severed and then discarded.

The threads are then twisted and tensioned in a path which extends through the heating zone of the electrical resistance heating wire 21, and as heat is supplied by turning on the current of the heating element, the outer surface of the twisted threads closest to the heating wire begins to melt first. There is a resulting reduction in tension on the threads caused by this melting which in turn results in the unwinding of the threads under torsional stress with further melting around the entire circumference until the originally twisted length of thread is severed. During this untwisting and melting operation the two distinct threads T and T, become joined at the point of melting, i.e. in the heated zone, and quickly fuse together and solidify as the two separated portions drop down out of the heating zone. The two joined threads are then easily removed laterally from the clamping device, and the shorter scrap length is also removed and discarded.

The resulting heat-welded or melt-bonded thermoplastic threads are firmly joined together over a very short length by this procedure, and the resulting joint is practically invisible and causes no serious difficulties in subsequent textile operations. Fabrics produced from such lengths of welded threads are of much higher quality than would otherwise be possible where thread ends project from the fabric or otherwise contribute to a poor appearance. At the same time, the apparatus and method of the invention permit a very economical and rapid means of uniting the ends of threads during large scale commercial operations.

EXAMPLE Two threads of nylon 6 were joined at their ends by welding with the device shown in the drawing. Each thread to be joined consisted of two smaller threads of 1,140 denier and 64 individual filaments doubled or twisted together with turns per meter. The interval between the clamping jaws amounted to 10 cm., and the interval between the heating wire and the closest clamping jaw was 3 mm. Also, the heating wire was arranged at an interval of about 2 mm. from threads or strand when tensioned between the clamping jaws.

The two thread ends to be joined were held parallel between the thumb and forefinger of both hands and then twisted together until the resulting strand exhibits a twist of about 2 to 3 turns per centimeter. The two twisted threads are fastened between the clamping jaws while held under tension and then released from the hands. The heating wire is then turned on. During the fusing of the individual filaments, the two stranded threads turn back again on account of the original twist imparted thereto, whereby the ends of the thread being melted come into mutual contact and are connected after cooling below their melting point.

The invention is hereby claimed as follows: 1. A method of uniting the ends of yarns or threads com posed of a thermoplastic filamentary material which comprises:

placing the ends of the threads to be united together in parallel relationship with the ends extending in the same direction;

twisting the threads over a short length of about 2 to 10 cm.

adjacent the ends thereof and with a twist of about I to 4 tums/cm. sufficient to cause the threads to untwist under the release of longitudinal tension;

clamping the twisted short length at either end thereof under longitudinal tension; and

continuously applying heat to a selected intermediate portion of the twisted length by direct contact of a heating element along one side of the twisted threads to simultaneously melt and untwist said threads under release of tension until the original twisted length is severed, the melted and twisted ends then being dropped out of contact with said heating element and being fused and solidified together the cooling below their melting point.

2. A method as claimed in Claim 1 wherein heat is applied by a heating element extending over an intermediate twisted length of about 0.5 to 4 mm.

3. A method as claimed in claim 2 wherein heat is applied to the twisted length of threads in a heating zone located approximately 1 cm. or less from the clamping position which is most remote from the thread ends.

4. A method as claimed in claim 2 wherein the twisted length of threads between clamping positions is about 4 to 8 cm.

5. A method as claimed in claim 2 wherein the intermediate length to which heat is applied amounts to not more than about 2 mm.

6. A method as claimed in claim 1 wherein the twisted length of threads between clamping positions is about 2 to 10 cm., heat is applied to the twisted threads with a heating element in a heating zone extending over an intermediate length of not more than about 2 mm. which is spaced up to about I cm. from the clamping position which is most remote from the thread ends.

asses 732 3; UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3: 5:99 D d October 26, 1971 Inventor(s) Richard Munzner It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 35, claim 1, "the cooling" should read by cooling Signed and sealed this 15th day of August 1972.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. A method as claimed in Claim 1 wherein heat is applied by a heating element extending over an intermediate twisted length of about 0.5 to 4 mm.
 3. A method as claimed in claim 2 wherein heat is applied to the twisted length of threads in a heating zone located approximately 1 cm. or less from the clamping position which is most remote from the thread ends.
 4. A method as claimed in Claim 2 wherein the twisted length of threads between clamping positions is about 4 to 8 cm.
 5. A method as claimed in claim 2 wherein the intermediate length to which heat is applied amounts to not more than about 2 mm.
 6. A method as claimed in claim 1 wherein the twisted length of threads between clamping positions is about 2 to 10 cm., heat is applied to the twisted threads with a heating element in a heating zone extending over an intermediate length of not more than about 2 mm. which is spaced up to about 1 cm. from the clamping position which is most remote from the thread ends. 